Patent GB-428206-A (GB)
Title: Improvements in or relating to apparatus for producing sheet material of controlled thickness
Filed: 1933-08-29
Abstract: 428,206. Gauges. FIRESTONE TYRE & RUBBER CO., Ltd., Great West Road, Brentford, Middlesex.-(A s - signees of Brown, R. W.) Aug. 29, 1933, No. 23933. Convention date, Sept. 24, 1932. [Class 106 (ii)] [See also Groups V and VIII] In the continuous production of sheet material such as rubber, or proofed fabric, the thickness of the sheet is periodically gauged, and the sheetforming apparatus is automatically adjusted to compensate for variations in the thickness of the sheet. Riding on the work W, Fig. 1, as it passes round the bowl 32 of a calender A, is a trolley 65 pivoted at 71, and held against the work by a weight 76. On the trolley is mounted an open-core transformer of which the bowl 32 forms an armature spaced therefrom by the sheet W. A similar transformer 80, Fig. 12, is mounted in a frame 85 at the back of the instrument shown in elevation in Fig. 11, and housed in a cabinet D, Fig. 1. The frame 85 is attached at one side to the casing by a flexible hinge 86 : at the other side, the frame is pressed by a spring 94 against a screw 90. Adjustment of the transformer 80 in relation to its armature 97, is made by means of a worm 115<a>, Fig. 12, engaging a wormwheel 113 on a spindle carrying a fork 109 which embraces a finger 108 on the screw 90. A dial 118, Fig. 11, with spiral groove 119 carrying an indicator 121 shows the setting of the transformer, and a pen 129 operated through a bell-crank lever 127 by a nut 130 on a screw 115, records this on a travelling band 133. The primary circuits of the two transformers are connected in series. The secondary currents heat thefmo - couples, the currents from which are balanced against one another on a bridge including a galvanometer 140, Fig. 11. Variations in the gap of transformer 60, cause a deflection of the galvanometer coil and its pointer 143. When deflected, the pointer 143 passes under one of the arms 145, 146, of pivoted levers having depending arms in contact with a friction clutch member 156 mounted on an arm 154. Periodically, a cam 159 on a shaft 151 driven by a motor 153, lifts the clutch member clear of its disc 157. At the same time a cam 150 raises a bar 149, and with it the galvanometer pointer 143. If the galvanometer is balanced, the pointer rises between the levers 145, 146 ; otherwise one of these levers is tilted, the amount depending on the deflection of the pointer, and the clutch bar 156 is moved out of the horizontal, bringing one of its ends into the path of one of two cams 160 on the shaft 151. The cam 159 then allows the clutch member 156 to contact with the disc 157, and the rotation of the cam 160 restores the clutchbar 156 to the horizontal, with a partial rotation of the disc 157. On the shaft of this disc are mounted, (a) a disc 161, Figs. 11, 12, to which are attached cords 162 operating a pen 164 on the band 133 ; (b) cam surfaces 167, 168, 169 which operate switches 170, 171, 172, to light lamps 173, Fig. 1, when the work is under, at, or over gauge respectively ; (c) an arm 177 operating a screw 101 to move the armature 97, mounted between a flexible hinge 99, and spring 106, to restore the balance between the transformers 60, 80 ; (d) a contact moving over a rheostat 180 controlling the current to a variablespeed motor 217, Fig. 18, operating the calender adjusting devices. The motor runs constantly, and rotates a sleeve 224 through a gear 223, the motor being driven fastest when the work is on gauge. Bearing on the sleeve 224 is an idler roll 226, which bears also on a friction disc 225. When the work is on gauge, the circuit closed by the switch 171, Fig. 12, energizes a solenoid 231 to draw the idler into the position shown in dotted lines, and so cause the disc 225 to rotate at a higher speed. When the work is off gauge, a spring 234 draws the idler into the position shown in full. The disc drives three cams 255, 256, 257, which operate respectively mercury switches 267, 327, and 325 and 326. On rotation of the cam 255 through the sixth of a revolution, the switch 267 is tilted, closing a circuit to energize a solenoid 243 which attracts an armature 242 pivoted at 238, to lift a shaft 227 on which is mounted the idler 226 to clear the sleeve 224, apply a brake 241, and stop the mechanism. The switch 267 is operated to break the circuit of solenoid 243 by the lifting of a bar 275 attached to the armature of a solenoid 277 which is operated through a mercury switch 280, Fig. 11. This switch is held open by a catch 296 when the work is on gauge. When off gauge, solenoid 293 is energized to withdraw the catch and free a plate 283 which can drop into a slot in a disc 284 driven through gearing from the shaft 151 at such a rate that the disc makes one revolution for an exact number of gauging operations. This closes switch 280, energizes solenoid 277 to tip the switch 267 to break the circuit of solenoid 243 and allow a spring 244 to pull the idler into contact with the sleeve 224 and rotate the disc 225, and consequently the cams 255, 256, 257, through a sixth of a revolution when the switch 267 is again closed. The cam 256 operates a switch 327 to supply current to the coil of an electromagnetic clutch driven by a reversible motor 45 which runs in the appropriate direction for adjusting the calender through gears 46, 44 and worm-wheels 40, 49, when the work is off gauge, and switch 170, or 172, Fig. 12, is closed. The cam 257 operates two switches 325, 326, one of which 326 closes a contact to a magnetic brake and 325 to pass a small current to the clutch to produce a drag, and take up back-fash in the calender adjusting gear before the next operation. A mercury switch in the unit 60, Fig. 1, stops the operation when the transformer is swung out of action. A generator 201 driven by the work W, drives a motor on which is mounted a centrifugal mercury switch which breaks the circuit should the speed of the calender fall below a minimum. Should the circuit be broken just before, or during a calender adjustment, current is supplied by a switch 300 Fig. 11, controlled by a cam 303 on the same spindle as the cam 284 which controls switch 280, to complete the adjustment and then bring the apparatus to rest.